I got a 3f ul gear pack from aliexpress - Trajectory 55 (beware they have several versions but all the others look too complicated with using a pad or no stretchy side pockets etc....) - for trying this kind of "ul" backpack (I know already that I am not a huge fan of rolltop closures but I like the huge outer pockets). It wasn't super cheap but with Xpac fabric - which in my experience with a hip belt pouch is pretty durable. And some kind of padding at the back.
Only used it for a city trip with day trips which works fine (without the aluminum inserts to make sure that it meets the requirements for carry-on). It is a bit narrow so it would build up higher than I like when full, but on the other hand your gear should be "adjusted" for this kind of backpack as well. I guess it performs better with the inserts, generally you have to put more effort into packing accordingly.
Last edited by Kokanee75; 12-09-2019 at 11:35 PM.